Copper-nickel-aluminum alloy and method of heat treating the same



Patented A r. 22, 1930 UNITED STATES PATENT OFFICE WILLIAM A MUDGE, 0F HUNTINGTON, WEST VIRGINIA, ASSIGNOR, BY MESNE AS- SIGNMENTS, TO THE INTERNATIONAL NICKEL COMPANY, INC., OF NEW YORK,

N. Y.,' A CORPORATION OF DELAWARE COPPER-NICKEL-ALUMINUM ALLOY AND METHOD OF HEAT TREATING THE SAME No. Drawing. Original application filed March 31 1925, Serial No. 19,730. Divided and this application fi1ed July 13, 1925.

My invention relates to the treatment of alloys containing as their main ingredients nickel, copper and aluminum, wherein the aluminum is from about .1% to 17% (from about 2% to 7% preferred); the cooper is from about 1% to 90% .(preferably over 10%) and the remainder is mamly nickel (the nickel preferably bemg over about 40%). Such alloy may and usually does contain small amounts of other elements, such as iron, manganese, carbon, etc.' The manganese may increase somewhat, thus, of course, correspondingly decreasing slightly the proportions of the main alloying elements.

I have discovered that an alloy of the above nature may be materially changed and improved in physical properties by proper heat While the exact physical andtreatment. chemical reasons underlying this phenomenon are not known to me at present, I believe that the change in physical properties is probably due to the formation by such treatment of a compound of copper and'aluminum or possibly a compound of nickel, copper and aluminum. Apparently the amount of such compound or compounds formed vary with the difi'erent compositions and the heat treatment and may account for the variations noted in the physical properties.

In a long series ofexperiments on heat treatment of this material, I have made the following discoveries:

If the material has been quenched from a temperature of 1500 F. and above, it will dead soft. heated, I have found the following facts:

(a) Up to about 600 F., there will be practically no change in the physical properties. I I p (6) Between 600 F. and 1000 F., a

. gradual increase in desirable physical prop- If such dead soft material is Serial No. 43,404.

ness will be increased, while the elongation and reduction of area will be decreased.

The above statements apply regardless of the rate of cooling, but slow cooling from any of the temperatures above mentioned will, in general, give better physical properties than when the material is rapidly cooled from these same temperatures, as for example, by quenching in oil or water or in any other suitable quenching medium.

If the material is heated to a temperature above '1200 F., there will be a decrease in these physical properties, and this decrease will be proportional to the increase in temperature from 1200 F. up to below 1800 F. Also the rate of cooling will afl'ectthe desired physical properties in this case. When rapidly cooled or quenched, the desired properties will be slightly lower than when slowly cooled from the same temperature. Also there is a time eflect in the heating, since extendingthe time of heating tends to increase the desired physical properties. For example, using dead soft material and one hours heating at the best temperature of about 1100 F., would give a semi-hard ma terial, whether cooled slowly or rapidly,-

' whereas if this heating at the same temperature on the same material was continued for eight or or more hours, a hard material will be produced having physical properties considerably in excess of those produced in one hours heat treatment; and this again, whether the cooling is rapid or slow.

Continue heating at the maximum temperature of about 1100 F. for more than eight hours will slightly, but definitely increase the physical properties regardless of the rate of cooling.

As a specific illustration of these treatments, I will recite the following example, the material treated being composed of about 45% of nickel, %of copper and 4% of alu-- Heating at 1100 F. increased the proportional limit from 30,000 psi. to 80,000 psi. at the end of three hours. limit was further raised to 95,000 psi. at the end of the fifth hour. Longer heating at 1500 F. or an equal period of 1750 F., when followed by quenching, will reduce the proportional limit of the original material to 20,000 psi. In this event, a longer heating period at 1100 F. will be required to increase the proportional limit to 95,000 psi.

In this case, all the heating was carried out at 1100 F. and followed by slow cooling in air, but similar results might have been accomplished by rapid cooling following the same heat treatment.

'It will be noted from this example that starting with an original material of high physical properties, the heat treatment re.- duces these physical properties to a minimum and then raises them beyond the original values, all by heat treatment and without mechanical working.

Second emampZe.When this alloy has been hardened and the desired physical properties developed to a high value by the heat treatment, such as before described, it may be heated in the following ways without affecting its properties:

(a) To any temperature not to exceed 1200 F. with slow cooling.

(6) To any temperature not to exceed 1100 F. with quenching or quick cooling.

This discovery is important, especially in using the material in locations where it is subjected to variations in temperature conditions, as for example, when used for steam turbine blades. .The maximum temperature in turbine work is lower than the above points, and hence, the material will retain its desired physical properties under these conditions, even under wide variations of temperature. In other words, intermittent service at or below these temperatures does not materially change the characteristics of the material, if tested when cooled down.

If the material is heated above these temperatures, a decrease in the desired physical properties will 'result, without regard to the rate of cooling, but if the material is slowly cooled after such heating, it will have higher properties than if quenched after heating to above such temperatures.

Third example-If this hardened material is heated to a point between 1200 and 1500 F., a semi-hard material will be produced, regardless of the rate of cooling, al-

though the slowly cooled material in this case will be slightly harder than the quenched or rapidlycooled material. If this hardened material is heated to above 1500 F., and quenched or rapidly cooled, it will produce dead soft material, while slowly cooling itfrom a temperature of 1500 or above will produce a semi-hard material The proportional Using the same methods of heat treatment described in the examples noted above, the proportional limit of an alloy containing 90% nickel, 5% copper and 4.5% of aluminum has been varied between 20,000 psi. and 63,000 psi. The same heat treatment permits a variation with an alloy containing 85% nickel, 10% copperand 4% aluminum of 20,- 000 psi. to 85,000 psi. The same heat treatment again permits a variation with an alloy containing 80% nickel, 15% copper and 5% aluminum of 30,000 psi. to 120,000 psi. The same heat treatment again permits a variation with an alloy. containing nickel, 25% copper and 4% aluminum of 25,000 psi. to 105,000 psi.

I have found. that the optimum hardening temperature is about 1100 F., when followed by slow cooling in air, apparently regardless of the specific chemical composition of the alloy.

The above examples recite the major discoveries which I have made in my heat treatment research on such alloys. I will now describe certain other features which'I have found in this research.

Either the dead soft or semi-hard alloy, when these properties have been imparted by the proper heat treatments, can be machined or fabricated with about the same case as a similar nickel-copper alloy containing no aluminum.

If the material is hardened and has the desired physical properties to a high degree, it is machined with considerable difficulty. Therefore, any one machining or fabricating this material while relatively cold and without material heating to obtain a certain article or device, would probably desire it in soft or semi-hard condition for such treatment; and thereafter the desired physical properties can be imparted by heating at from 1000 to 1200 F., the properties increasing with the length of heating, as above described, and being preferably followed by a slow cooling to bring these properties to their highest value.

Where the material is worked in hot con dition for sale in merchant shapes, the best practice would probably be to roll or forge it at a temperature between 1800 F. and about 2150 F., with ordinary slow cooling in the air. This will give a semi-hard product, without any further treatment, and if the customer desires a dead soft material, the material as rolled or otherwise hot worked should be quenched or quickly cooled from a temperature of 1500 F. to give a soft material.

If, on the other hand, there is desired a very hard alloy possessing the desired physical properties to a high degree, the best practice. is to allow the material to cool slowly after.-

F., for several hours and allow it to cool slowly in the air. As above pointed out, the longer this, heating extends within certam limits, the more of the compound will be formed and the greater the physical characteristics.

Vhile I do not know definitely the chemical or physical reasons underlying the phenomena, it seems reasonable to suppose that the hardness and other desired physical properties may be due to the gradual formation of a copper-aluminum compound or possibly a nickel-copper-aluminum compound during the heating.

I have also found that where the desired properties are imparted, either to a high degree or to a medium degree, these properties are slightly improved by aging of the ma terial. Thus, where the material had been quenched from 1500 F. andabove, to produce dead soft material. the proportional limit being reduced from 80,000 psi. to 25,000 psi.,,this material was heated at about 1100 F. for one to three hours, and some samples quenched and others slowly cooled.

In both cases. one sample was tested about five minutes after cooling and another about twelve weeks after cooling. The aged samples from both the quenching and the slow cooling were found to be improved in proportional limit and hardness by from 5% to 15%. v I My improved heat treatment is, of course, applicable to, a nickel-copper-aluminum al- 10y containing .1 to 17% of aluminum, whether in the cast condition or when worked hot or cold or machined.

This case is a division of my copending I application, Serial No. 19.730. filed March 31,

1925, for manufactureof alloys of copper, nickel and aluminum. In the present case, I intend to cover my invention wherein the material is heated to over 1200 F. and slowly cooled. and more specifically,'whereit is hea ed to 1500 or over and slowly cooled. I a so intend to cover herein the resulting pro not which is semi-hard. as well as the 'aluminum and at least 15% of nickel, the

step of subjecting the material to regulated cooling" from a temperature of over 1500 F. but short of melting.

3. In the treatment of nickel-copperaluminum alloys containing up to 17% of ct having a certain range-or psi. By

aluminum and at least 15% of nickel, the step consisting of heating the material to a temperature of over 1200 F. and short of melting and slowly cooling it.

4. In the treatment of nickel-copperaluminum alloys containing up to 17% of aluminum and at least 15% of nickel, the steps consisting of heating the material to a temperature of over 1500 F. and short of melting and slowly cooling it.

5. In the treatment of nickel-copperaluminum alloys containing up to 17% of aluminum and at least 15% of nickel, the step consisting of rapidly cooling the heated alloy to soften it and then reheating it to over 1200 F. and short of melting and allowing it to cool.

6. In the treatment of nickel-copperaluminum alloys containing up to 17% of aluminum and at least 15% of nickel, the 85 steps consisting of rapidly cooling the heated alloy to soften it and then reheating it to over 1200 F. and short of melting and slowly cooling it. a

7. As a new article of manufacture, a semihard alloy of nickel. copper and aluminum containing from 2% to not over 17% of aluminum and at least 15% of nickel and having a physical structure such as is produced by regulated cooling of an alloy of this composition which has been heated to a temperature of over 1200 F. but short of' melting.

8. As a new article of manufacture, a semi-hard alloy of nickel, copper and alumion num containing from 2% to not over 17% of .1 aluminum and at least 15% of nickel and having a physical structure such as is pro-- duced by regulated cooling of an alloy of this composition which has been heated to a temperature of'over 1200 F. but short of melting and having a proportionallimit of 40.000 to 80,000 psi.

9. In the treatment of nickel-copperaluminum alloy containing less than 20% of aluminum and at least 15% of nickel. the steps consisting of heating the material to above 1500"v F. and allowing it to slowly cool.

10. In the treatment .of nickel-copperaluminum alloy containing less than 20% of aluminum and at least 15% of nickel, the steps consisting of subjecting it to a slow cooling from a heated condition to harden it and improve its physical properties, the temperature suflicient to harden the material when slowly cooled. v

11. In the treatment of nickel-copperaluminum alloy containing less than 20% of aluminum and at least 15% of nickel. the steps consisting of heating the material to over 1500 F. and subjecting it to regulated cooling I In testimony whereof I have hereunto set my hand.

' WILLIAM A. MUDGE. 

